11 replies to this topic

[stonestudded]

and.... what is PLC exactly? i know i'm a mountain turtle as i'm rather new to this industry and i hope fellow members could help me out. Thanks in advance.

Edited by stonestudded, 11 April 2006 - 11:18 AM.

[kongming]

and.... what is PLC exactly? i know i'm a mountain turtle as i'm rather new to this industry and i hope fellow members could help me out. Thanks in advance.

Although I am no expert in this area, PLC stands for 'Programmable Logic Controllers'. It is primarily a device that can be programmed by hardware or software to perform certain tasks under different conditions and basically uses a binary format (logic '1' or '0') to form a series of actions that controllers will take depending on the '1's and '0's.

Programming the PLCs often is done with certain software to make the job easier, and usually engineers will be trained in PLC programming as one of their modules in schools.

OF course, the usuage of PLC is very wide, ranging from controllers of robotic arms to controller of different inputs and outputs. This area being not the expert on PLCs, I do not have examples to give, and I believe the industry leaders here can give more information about PLCs

[wolfie]

Although I am no expert in this area, PLC stands for 'Programmable Logic Controllers'. It is primarily a device that can be programmed by hardware or software to perform certain tasks under different conditions and basically uses a binary format (logic '1' or '0') to form a series of actions that controllers will take depending on the '1's and '0's.

Programming the PLCs often is done with certain software to make the job easier, and usually engineers will be trained in PLC programming as one of their modules in schools.

OF course, the usuage of PLC is very wide, ranging from controllers of robotic arms to controller of different inputs and outputs. This area being not the expert on PLCs, I do not have examples to give, and I believe the industry leaders here can give more information about PLCs

Actually, looking at the industry, there are so many companies selling different brands of PLCs, so basically the other question I wanted to ask is, 'IS there any difference in PLCs specifications provided by different companies? If so, what's the difference between the PLCs provided by different vendors? Would the different companies share a bit about their brand of PLC?'

[CYC]

Actually, looking at the industry, there are so many companies selling different brands of PLCs, so basically the other question I wanted to ask is, 'IS there any difference in PLCs specifications provided by different companies? If so, what's the difference between the PLCs provided by different vendors? Would the different companies share a bit about their brand of PLC?'

Actually, to answer your question, imagine PLCs as cars/vehicles. Why are there so many types/models/make, etc..? The answer is simply every manufacturer wants a share of the cake in the market and begin to develop their own products.

Basically, they are all similar in term of functionalities. Again, like buying cars, some customers prefer automatic gears but some prefer manual. There are of course some features in some PLCs others might not have. Importantly, the service and support from the manufacturer and/or supplier.

I suggest you take up a basic course on PLC where you will understand the concept and fundamentals. The confusing part is every PLC manufacturer have their own programming addresses so that once you are familiar with one type, you will prefer using it most of the time. I hope that answers your question and clear your doubts. By the way, are you student or working adults or perhaps fresh graduate.

CYC

[Johnson Lukose]

PLC - Programmable Logic Controller.

PLC's was invented by Richard E Morley who also founded Modicon (now part of Schneider Electric). In fact he called it PC - Programmable Controller. It was Allen-Bradley years later who coined PLC - Programmable Logic Controller. So for a while there were two inter-changeable names in the market PC & PLC!

With the advent of the PC market, PC as in Personal Computer - the question was settled by the markets. PC - Personal Computer and PLC - Programmable Logic Controller.

So Modicon was the first PLC company in the world. But Allen-Bradley the MS of industrial automation (bigger marketing budget and empty up-manship) always claim they invented the PLC because they coined the term first.

An excerpt introduction reads - "Richard E. Morley, the CEO of Flavors Technology, Inc., is the founder or co-founder of more than ten companies, including Modicon and Andover Controls. A nationally recognized expert in the fields of computer design and artificial intelligence, and a leading authority on the application of chaos theory in manufacturing, Mr. Morley holds more than twenty patents, including one for the Programmable Logic Controller, now housed in the Smithsonian Institution."

thanks.

[Praetorian]

PLC - Programmable Logic Controller.

PLC's was invented by Richard E Morley who also founded Modicon (now part of Schneider Electric). In fact he called it PC - Programmable Controller. It was Allen-Bradley years later who coined PLC - Programmable Logic Controller. So for a while there were two inter-changeable names in the market PC & PLC!

With the advent of the PC market, PC as in Personal Computer - the question was settled by the markets. PC - Personal Computer and PLC - Programmable Logic Controller.

So Modicon was the first PLC company in the world. But Allen-Bradley the MS of industrial automation (bigger marketing budget and empty up-manship) always claim they invented the PLC because they coined the term first.

An excerpt introduction reads - "Richard E. Morley, the CEO of Flavors Technology, Inc., is the founder or co-founder of more than ten companies, including Modicon and Andover Controls. A nationally recognized expert in the fields of computer design and artificial intelligence, and a leading authority on the application of chaos theory in manufacturing, Mr. Morley holds more than twenty patents, including one for the Programmable Logic Controller, now housed in the Smithsonian Institution."

thanks.

Wow, that's a great deal of knowledge, historical I mean... And how true is this???

Johnson, anywhere can I get the facts on your statement???

[Johnson Lukose]

Wow, that's a great deal of knowledge, historical I mean... And how true is this???

Johnson, anywhere can I get the facts on your statement???

You can always search the net... Google

but as for me,

the information is from the mouth of Richard E Morley. We were at a conference together for a week. I spent every minute I could to learn from this remarkable man.

thanks.

[Johnson Lukose]

Actually, looking at the industry, there are so many companies selling different brands of PLCs, so basically the other question I wanted to ask is, 'IS there any difference in PLCs specifications provided by different companies? If so, what's the difference between the PLCs provided by different vendors? Would the different companies share a bit about their brand of PLC?'

There actually was too many differences and distinctions to note. However, the bigger manufacturers dominated and the smaller ones followed the general direction...

The users of PLC systems was also as confused as you...

But the difference was some of these users were GM, Daimler Benz, Peugeot, etc. who were bigger companies than the PLC vendors... ha, ha, ha!!

However, in ~1990 a new standard from who else but IEC started taking shape. First called IEC1131 then renamed IEC61131 - is the new standard for PLCs. Many RTU and DCS manufacturer also follow this standard for the I/O cards and in many cases the programming implementation too. The standard is broken down into several sections.

The following is an excerpt from www.plcopen.org. There is a wealth of information at this website.

IEC 61131-1 General information
establishes the definitions and identify the principal characteristics relevant to the selection and application of programmable controllers and their associated peripherals <<for the IEC overview and table of content, click here..>>;

IEC 61131-2 Equipment requirements and tests
specifies equipment requirements and related tests for programmable controllers (PLC) and their associated peripherals <<for the IEC overview and table of content, click here..>>;

IEC 61131-3 Programming Languages -
providing the basis defines, as a minimum set, the basic programming elements, syntactic and semantic rules for the most commonly used programming languages, including graphical languages of Ladder Diagram and Functional Block Diagram, and Textual languages of Instruction List and structured Text; as well as major fields of application, applicable tests and means by which manufacturers may expand or adapt those basic sets to their own programmable controller implementations <<this website is mostly dedicated to IEC 61131-3, and contains a lot of information on it - check it out via the overview on your left side. For the IEC overview and table of content, click here.. For the PLCopen introduction, click here>> - or in word format. or (zipped) power point. For evaluation of software, click here.

IEC 61131-4 User Guidelines
A technical report providing general overview information and application guidelines of the standard for the end user of programmable controllers <<for the IEC overview and table of content, click here..>>;

IEC 61131-5 Messaging service specification
defines the data communication between programmable controllers and other electronic systems using the Manufacturing Message Specification (MMS, according to International Standard ISO/IEC 9506 <<for the IEC overview and table of content, click here. For the PLCopen introduction, click here..>>;

IEC 61131-7 Fuzzy control programming
defines basic programming elements for fuzzy logic control as used in programmable controllers <<for the IEC overview and table of content, click here. For the PLCopen introduction, click here..>>;

IEC 61131-8 Guidelines for the application and implementation of programming languages
provides a software developers guide for the programming languages defined in part 3 <<for the IEC overview and table of content, click here..>>.

(Note: Part 6 is reserved for future use.)

With this standard, the differences and distinctions have largely narrowed. Also the differences and distinctions have largely narrowed due to consolidation of the manufacturers.

thanks.

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[jaxrobinson]

PLC is programming logic controller.

[scott_white85]

PLC stands for programmable logic coontroller which is usually used for electromechanical and automation processes. this is a small computer which has the ability to control the system. it can easily run many machines. troubleshooting is very quick, simple and easy.

[craigwilson]

Programmable Logic Controller, a control device that consists of a programmable microprocessor. mostly used in industries for control and automation.
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